public List<Token> Lex(string str)
{
List<Token> TokenList = new List<Token>();
int iter = 0;
while(true)
{
while (iter < str.Length && Char.IsWhiteSpace(str[iter]))
iter++;
Token token = new Token();
if (iter >= str.Length)
{
TokenList.Add(token);
break;
}
else if (Char.IsNumber(str[iter]))
{
while (iter < str.Length && Char.IsNumber(str[iter]))
token.Text += str[iter++];
token.Id = Token.TokenId.Number;
}
else
{
token.Text += str[iter++];
if (operators.Contains(token.Text))
token.Id = Token.TokenId.Operator;
else
token.Id = Token.TokenId.Unknown;
}
TokenList.Add(token);
}
return TokenList;
}
public INode Parse(List<Token> Tokens)
{
iter = 0;
tokens = Tokens;
token = Tokens[iter++];
INode node = SumSub();
if (token.Id != Token.TokenId.END)
throw new Exception("There is an excess part of expression");
return node;
}
public INode Term()
{
INode node = null;
if (token.Id == Token.TokenId.Number)
{
node = new ValueNode(double.Parse(token.Text));
token = tokens[iter++];
}
else if (Accept("("))
{
node = SumSub();
if (!Accept(")"))
throw new Exception("Unmatched parentheses");
}
else if (token.Id == Token.TokenId.Unknown)
throw new Exception("unknown token " + token.Text);
else if (token.Id == Token.TokenId.END)
throw new Exception("Unexpected end of expression");
else
throw new Exception("Unexpected token " + token.Text);
return node;
}
private bool Accept(string str)
{
if (token.Text == str)
{
token = tokens[iter++];
return true;
}
else
return false;
}